Document Type : Research Paper

Authors

• Mohammad Ghaffari-Sola ¹
• Hamed Ketabchi ²
• Davood Mahmoodzadeh ³

¹ Department of Water Engineering and Management, Tarbiat Modares University, Tehran, Iran

² Associate Professor, Department of Water Engineering and Management, Tarbiat Modares University, Tehran, Iran

³ School of Engineering, University of Northern British Columbia, British Columbia, Canada

Abstract

Keywords

• Marvdasht aquifer
• Fars province
• recharge estimation
• finite difference method
• groundwater modeling

Main Subjects

• منابع آب

EXTENDED ABSTRACT

Introduction

Groundwater resources are a vital source of freshwater worldwide, especially in arid and semi-arid regions. The over-extraction of groundwater can have significant consequences and pose a potential threat to human life and survival. Therefore, it is essential to manage the use of these resources in a way that ensures their sustainability and prevents damage to their balance. One effective approach for evaluating the sustainability and management of groundwater resources is through the estimation of groundwater balance and the analysis of water table fluctuations.This approach quantitatively determines the groundwater system's inflows, outflows, and water table fluctuations. Also, this approach provides managers/policymakers with the tools to make informed decisions and plan effectively for these resources. There are various methods for evaluating and estimating the groundwater balance. One such method is numerical modeling, which has been widely used in many studies as an effective and efficient tool for assessing the groundwater balance and water table fluctuations, demonstrating satisfactory performance. This study aimed to develop a numerical groundwater model to assess and estimate the changes in groundwater levels and their fluctuations and the aquifer balance in a real region within Fars Province.

Material & Method

This study evaluates and analyzes the water balance changes and groundwater table fluctuations of the Marvdasht aquifer in Fars Province using a finite-difference mathematical modeling approach. The model is designed as a two-dimensional, single-layer representation of the groundwater system. The simulation period spans 15 years, covering the hydrological years from 2004 to 2018. For the model, both calibration and validation processes were conducted to minimize the differences between simulated and observed water table levels at observation wells.Finally, after completing the calibration and validation processes, the model was employed to predict and evaluate groundwater table levels for the next 15 years.

Results

Data from 54 observation wells in the study area were used to detemine the aquifer’s hydrograph over a 15-year period. The results show that groundwater levels declined by an average of 20 meters during the simulation period. The model calibration was conducted using recharge parameters dependent on return flow and rainfall infiltration coefficients, hydraulic conductivity, transmissivity, inflow and outflow rates at the boundaries. The rainfall infiltration coefficient set to 23% for all grid cells and the return flow coefficient varying between 20% and 50% across different sections of the region. During the 15-year simulation period, 12 years were used for calibration and 3 years for validation, and the model was evaluated using RMSE, ME, and MAE metrics. The results of RMSE = 0.65 m, ME = -0.58 m, and MAE = 0.58 m were calculated for the calibration period and RMSE = 0.12 m, ME = 0.24 m, and MAE = 0.24 m were calculated for the validation period, indicating that the model successfully simulated and estimated groundwater levels. The simulation revealed a -46.7 million cubic meter change in aquifer storage, and of the management scenarios applied to predict the aquifer's future status, two scenarios had positive impacts, improving groundwater levels and water balance, while two scenarios had negative impacts, leading to further declines, with the maximum groundwater level decline recorded at 17 meters and the maximum rise at 11.7 meters across the study area. On a long-term average, the contributions to recharge were estimated as total recharge at 421.55 million cubic meters, rainfall infiltration at 62.75 million cubic meters, surface water infiltration at 145.54 million cubic meters, and return flow at 213.25 million cubic meters.

Conclusions

In this study, a finite difference mathematical simulation model was employed to simulate groundwater level fluctuations and the water balance of an actual aquifer study area. After calibrating and validating the model, four management scenarios were applied to predict and evaluate the aquifer's status. Among the scenarios, transitioning irrigation systems from traditional surface irrigation methods to pressurized irrigation systems reduced groundwater levels by 17 meters in the scenario-affected region, while reducing groundwater extraction by 50% compared to current conditions led to an increase in groundwater levels by 11.7 meters across the study area. These findings highlight the significant impact of improved irrigation practices and controlled water extraction on the sustainability of aquifer resources.

Author Contributions

Conceptualization, H.K., D.M. and M.G.; methodology, H.K.; software, M.G.; validation, H.K. and D.M.; formal analysis, H.K., D.M.; investigation, M.G.; writing—original draft preparation, M.G.; writing—review and editing, M.G., H.K. and D.M.; visualization, M.G.; supervision, H.K., D.M.; project administration, H.K., D.M.;

Data Availability Statement

Not applicable

Acknowledgements

The authors would like to thank all participants of the present study.

Ethical considerations

The authors avoided data fabrication, falsification, plagiarism, and misconduct.